Rock Identifier
Agate (Chalcedony (SiO2)) — mineral
mineral

Agate

Chalcedony (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7; Color: banded or multicolored (often reddish-brown with white quartz/chalcedony centers); Luster: waxy to vitreous; Crystal structure: cryptocrystalline; Cleavage: none; Specific gravity: 2.58-2.64.

Hardness
6
Luster
waxy to vitreous
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Physical properties

Hardness: 6.5-7; Color: banded or multicolored (often reddish-brown with white quartz/chalcedony centers); Luster: waxy to vitreous; Crystal structure: cryptocrystalline; Cleavage: none; Specific gravity: 2.58-2.64.

Formation & geological history

Forms in cavities of eruptive rocks or ancient lavas from silica-rich groundwater over thousands to millions of years.

Uses & applications

Commonly used in lapidary arts, jewelry, and tumbling for collectors.

Geological facts

Lake Superior agates are famous for their rich red, orange, and yellow banding, caused by iron oxidation.

Field identification & locations

Identify by its waxy luster, translucency (especially on edges), conchoidal fracture, and often banded appearance. Look in gravel pits, riverbeds, and beaches.

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